1. Field of the Invention
The present invention relates to a process for production of a carboxylic acid ester and formamide. More particularly it pertains to a process for efficiently producing a carboxylic acid ester and formamide from a carboxylic acid amide and formic acid ester or from a carboxylic acid amide, an alcohol and carbon monoxide (hereinafter referred to as "Carboxylic acid amide and Formic acid ester, etc." including the above two combinations).
2. Description of Related Art
Carboxylic acid esters are industrially important compounds. As the processes for producing a carboxylic acid ester from a carboxylic acid amide, there are available, for example, the process for production of methyl acetate from acetic acid amide, that of methyl methacrylate from methacrylic acid amide, that of methyl acrylate from acrylic acid amide, that of methyl .alpha.-hydroxyisobutyrate from .alpha.-hydroxyisobutyric acid amide.
Formamide is used as a solvent, a treating agent, an electrolyte, an antifreezing agent, a starting material for producing hydrogen cyanide or as an intermediate for production of a medicine, a dye, a pigment or for organic synthesis.
As the process for producing a carboxylic acid ester from a carboxylic acid amide, there has heretofore been known a process wherein a carboxylic acid amide is reacted with an alcohol in the presence of sulfuric acid, which process has been widely put into practice for the industrial production of methyl methacrylate. However, the aforesaid process is confronted with such problems as the production of a large amount of acidic ammonium sulfate, a high cost required for the disposal thereof and the necessity of expensive corrosion-resisting equipment.
As the process without the use of sulfuric acid, there is proposed, for example, in Japanese Patent Application Laid-Open Nos. 14452/1978, 141216/1978, etc. a process wherein a carboxylic acid ester is produced by the catalytic reaction of a carboxylic acid amide with an alcohol. The aforementioned process, however, involves various problems in industrial application such as the low yield and low selectivity of the objective carboxylic acid ester, the formation of a large amount of ammonia necessitating the separation and recovery thereof and the formation of an ammonium salt by the reaction with a by-produced carboxylic acid.
As the process without the formation of ammonia, there is disclosed in Japanese Patent Application Laid-Open Nos. 55444/1983 and 78937/1985 a process wherein a carboxylic acid amide is reacted with a formic acid ester instead of alcohol to produce the objective carboxylic acid ester and formamide. In the above process, however, it is necessary to separate or deactivate the catalyst immediately after the reaction as the reaction proceeds as an equilibrium reaction. In addition, the above process suffers the disadvantages that the catalyst system is expensive and requires complicated steps for the regeneration and recycling of the catalyst, since the catalyst is composed of a metal salt of an organic or inorganic acid or a metal chelate compound in combination with an organic compound containing nitrogen or phosphorus or of an amidine or tertiary amine combined with a metal carbonyl.
There is also proposed in Japanese Patent Application Laid-Open Nos. 255640/1990, 268137/1990 and 48637/1991 a process wherein a carboxylic acid amide is reacted with a formic acid ester to produce the object carboxylic acid ester and formamide by the use of a catalyst composed of a dehydration condensation product of an alkali metal alcoholate, an alkaline earth metal oxide or a carboxylic acid amide with an alkali metal hydroxide or an alkaline earth metal hydroxide. The above-mentioned catalyst is relatively inexpensive and does not necessarily require recycling of itself, but still involves the problem that the salt formed in the deactivation step of the used catalyst complicates the separation of itself.
As described hereinbefore, in spite of the various processes for production of a carboxylic acid ester which have been disclosed so far, none of them meets the industrial requirement at the present time. Nevertheless, the process for producing a carboxylic acid ester and formamide from a Carboxylic acid amide and Formic acid ester, etc. is industrially advantageous in many respects, and gives rise to the need for the development of a catalyst applicable to the process with excellent characteristics in many industrial aspects.
Under such circumstances intensive research and investigation were concentrated by the present inventors on the solution of the above various problems in the production of a carboxylic acid ester and formamide from a Carboxylic acid amide and Formic acid ester, etc.
As the result, it has been discovered by the present inventors that the use of a strongly basic anion-exchange resin as the catalyst in the aforesaid process enables the proceeding of the reaction under mild conditions and the production of the objective carboxylic acid ester with formamide with a high yield and high selectivity and further, greatly facilitates the separation, recovery and recycling of the catalyst. The present invention has been accomplished on the basis of the above-mentioned finding and information.